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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Re: BUF03, BUF04 or BUF634 (and DC offsets) posted by avian on April 24, 2003 at 09:44:30:
I'll add a few comments, as I have built the BUF-03 preamp and played with others.First, you are correct - buffers like the BUF-03 are run open loop in class A. Versus most opamps that run with incredible feedback numbers as a follower (60-100dB), and in many cases have class AB outputs.
For these reasons, I think I would use the BUF634. What is planned to be downstream?
If an AMP, does it have a DC blocking cap on the input? It is very unlikely a commercial amp would not. So if it does, you are fine, no need to have two blocking caps in a row. If it does not, and is some high falootin' pure DC design, you will need to control the DC on the output by using a Cap or opamp based DC servo.A servo will add to the complexity. There was an article a while back in Audio Amateur showing how to build a discrete output buffer with a servo that was pretty easy to build. It was by Christopher Paul, lates 80's. I built it on a breadboard, worked fine.
Make sure you put a small resistor on the output, say 10-100ohms, and you may want to also consider putting a small one right on the the input pin, again 10-100 ohms, to control oscillation. These suckers will actually run at 100MHz, I have tested them there, so HF decoupling and controlling oscillation is important.
Bob
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- Re: BUF03, BUF04 or BUF634 (and DC offsets) - BFitz 10:16:23 04/24/03 (0)
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